The present invention relates to a retrofocus projection lens system capable of making various types of aberrations small, and a multivision projection display apparatus into which a plurality of retrofocus projection lens systems are incorporated.
A conventional projection display apparatus is disclosed in, for example, Japanese Patent Kokai Publication No. 138386/1994. In this apparatus, since an image is projected onto a screen by a single image projector, it is difficult to make a depth of the apparatus small. Further, in order to make the depth of the apparatus small, a wide angle projection lens is required.
A wide angle lens is known in the art of single reflex camera, however the following additional features are required in the wide angle projection lens for the multivision projection display apparatus of a small depth.
(a) The wide angle projection lens can correct the distortion which is a particular problem with wide angle lenses satisfactorily.
(b) The wide angle projection lens has an adequate air gap for inserting a mirror for bending an optical path.
(c) The wide angle projection lens has a long back focal length for inserting a color synthesizing dichroic prism.
(d) In order to prevent a color shade of the projected image and the reduction of the peripheral light amount, the principal off-axis light beam on the liquid crystal panel side is parallel to the optical axis, namely, the projection lens system has telecentric characteristics.
(e) Despite the wide angle lens, it allows a sufficient peripheral illuminance ratio to be obtained.